Multi-variety seed meters are designed to switch seed varieties on the fly and process two or more varieties of seed through the same meter. In order to minimize mixing of varieties within the meter, processing of the currently metered variety must be discontinued for some period of time before the seed meter can be reconfigured to process the next variety of seed. This is also known as starving the meter of the current variety of seed before feeding the meter with the next variety of seed.
Due to their relatively low cost, optical sensors and capacitive proximity sensors are commonly used in agriculture. However, optical sensors are easily blinded by dust buildup from the seeds, the field and from the powdered graphite that is often used as a seed lubricant. In the case of capacitive proximity sensors, they are triggered falsely by buildups of powdered graphite on the sensor. Thus, the seed meter environment is not conducive to using the most cost-effective sensors currently available.